Paste a PGP public key (« BEGIN PGP PUBLIC KEY BLOCK » block): the tool shows its fingerprint, its creation date and all the identities (name and e-mail) it contains, with the date each was added. Everything happens in your browser.

In real life: gpg --show-keys, pgpdump, key servers (keys.openpgp.org, keyserver.ubuntu.com). A key keeps every identity ever added to it, even old ones: a pseudonym sometimes sits right next to a real name.